1. Field of the Invention
The present invention relates to a test apparatus, an adjustment apparatus, an adjustment method and an adjustment program. Particularly, the present invention relates to a test apparatus, an adjustment apparatus and an adjustment method that adjust the timings of signal input/outputs previous to a test process and an adjustment program therefor.
2. Related Art
A test apparatus for testing an electronic device delays an input signal to a device under test by means of a delay element, and tests whether the device under test normally operates within a predetermined specification even if the signal to be provided to the device under test is delayed is disclosed as, for example, in Japanese Patent Application Publication No. 2000-199781. Here, when input signals to the device under test are delayed, the input signals are delayed for each of the plurality of input terminals of the device under test in the same way, and the signals should be inputted to the input terminals at the same timing. Meanwhile, output signals outputted from the device under test are tested, the output signals outputted from the output terminals of the device under test should be captured into the test module at the same timing every output terminal.
However, the characteristic of the delay element or the wiring delay is varied for each terminal. Therefore, if the amount of delay set to the delay element is the same for each terminal, the timing of a plurality of input signals to be inputted at a time could be different from each other. Therefore, an adjustment process so-called as a calibration is provided previous to the test process of device under test in order to adjust to input signals to a plurality of terminals at a time. In such calibration, the test apparatus detects a phase difference, i.e. skew of the signal inputted/outputted to/from each terminal. Then, the test apparatus adjusts the amount of delay of the signal at each terminal so as to reduce the phase difference to substantially zero.
FIG. 1 shows an example of wiring to perform a calibration in a test apparatus. The test apparatus includes a pin resource 105 for each of terminals (P1-P3) of a device under test. Each pin resource 105 has a driver 110 and a comparator 120. The driver 110 provides a predetermined test signal to the device under test. The comparator 120 captures the output signal from the device under test. A fixture for short U1 that short-circuits wiring lengths L1, L2 and L3 between each of terminals P1, P2 and P3 at even intervals for a calibration is connected to each comparator 120. For example, the fixture for short U1 may be formed of a terminal similar to the terminal of the device under test 20 and may be mounted to an IC socket or a contact socket. Additionally, the fixture for short U1 may be formed of board in face-to-face contact with the electrode of a socket board without the IC socket, or may short-circuits the socket board.
Each driver 110 is connected to a comparator 120 of the other channel. Each length between a connection point P and a terminal P1, a terminal P2 and a terminal P3 is the same interval. Here, each comparator 120 may have a termination resistor (e.g. 50 Ω) with a switch. In this case, the comparator 120 at the driver 100 side that outputs an adjustment signal may turn off the switch of the termination resistor, and two comparators 120 that receive the adjustment signal may turn on the switch of the termination resistor and terminate at the termination resistor.
FIG. 2 shows a flow of processing to detect the phase difference of the signal at each terminal in the test apparatus. In order to perform a calibration, it is necessary to accurately detect the phase difference of the signal at each terminal. The summary of the processing will be described with reference to FIG. 2. The test apparatus outputs a signal for a timing adjustment (hereinafter referred to as adjustment signal) from the driver 110 of the terminal P2 to the comparator 120 of the terminal P1(S200). Then, the test apparatus causes the comparator 120 of the terminal P1 to detect the phase of the adjustment signal (S210). In order to detect the phase, a technique such as a strobe may be used.
Next, the test apparatus outputs the adjustment signal from the driver 110 of the terminal P3 to the comparator 120 of the terminal P1 (s220). Then, the test apparatus causes the comparator 120 of the terminal P1 to detect the phase of the adjustment signal (S230). The test apparatus calculates the difference between the phase detected in the S210 and the phase detected in the S230 (S240). The test apparatus can adjust the driver 110 of the terminal P2 and/or the driver 110 of the terminal P3 in order to reduce the phase difference to substantially zero. Additionally, if the above-described process is applied to a combination of the other terminals, the phase difference of all the drivers 110 and the comparators 120 can be reduced to substantially zero.
In the above-described technique for detecting the phase difference, each wiring length between the connection point and the terminal P1, the terminal P2 and the terminal P3 should be equal. Otherwise, the amount of signal delay from the driver 110 to the comparator 120 is different for each of the terminals, so that the phase difference could not be correctly calculated. That is, if there is any error of the amount of signal delay of each wiring, the accuracy of the calibration could be reduced.
Additionally, the test apparatus may include a plurality of drivers 110 and a plurality of comparators 120 grouped for each board. In such a test apparatus, even if the amount of delay from the driver 110 to the comparator 120 in the group is adjusted within a certain amount of level, the amount of signal delay from the driver 110 to the comparator 120 in the group could be increased because the physical condition such as a temperature condition between the groups is different from each other. In this case, it is difficult for the test apparatus to accurately calculate the phase difference.
Thus, the advantage of the present invention is to provide a test apparatus, an adjustment apparatus, an adjustment method and an adjustment program which are capable of solving the problem accompanying the conventional art. The above and other advantages can be achieved by combining the features recited in independent claims. Then, dependent claims define filter effective specific example of the present invention.